1. Field of the Present Invention
The present invention relates generally to the fluid flow monitoring devices, and more particularly to fluid flow meters of the type having a vane member positioned in a fluid flow path and movable in response to fluid flow through the path.
2. Description of the Prior Art
There are many types of previously known fluid flow monitoring having means for sensing the rate of fluid flow through the monitor housing, as well as means for providing a corresponding indication of the fluid flow rate sensed by the sensing means. A particularly advantageous form of fluid monitor comprises the type have a housing defining a flow path between a fluid inlet and an fluid outlet, and having a vane positioned within the path so that the vane position varies depending on the rate at which fluid flows through the housing. Such vane type fluid fow monitors are particularly advantageous for the reason that an indicator means, switches or pointer, can be directly coupled to the movable vane in order to provide a direct indication of the vane position, and thus avoids numerous moving parts which increase the expense and complexity of a flow monitoring device.
However, in the typical previously known vane type flow meters, the vane is resiliently biased toward a first position in which it closes the flow path through the flow meter. When fluid pressure against the vane opposes the resilient force retaining the vane in its first position, i.e. fluid flow from the inlet to the outlet of the flow path and the flow meter, the fluid force moves the vane and permits the fluid to pass through the flow meter. The rate of the fluid flow is registered on the indicator by corresponding movement of the indicator with the vane. However, once the vane has returned to its initial position, the fluid flow in the opposite direction is blocked because the vane closes the flow path through the flow meter. Thus, as long as the fluid flows only in one direction through the device, the flow rate can be properly indicated by the flow meter device.
However, in view of the foregoing, previously known vane type flow meters cannot be utilized in line with fluid conduits through which the direction of fluid flow changes. Rather, previously known fluid conduit systems in which fluid flows in opposite directions could not be monitored by a simple and inexpensive vane type flow meters unless a separate bypass conduit if fluidly connected to the line so that a second vane type flow meter can be installed to monitor flow in the opposite direction. Therefore the advantages of the previously known vane type flow meters are substantially offset by the need for separate bypass conduit in the fluid system as well as the added expense of an additional flow meter housing unit. Moreover, the separate units would each be attached to the separate conduits by connectors, and thus increases the costs and complexity in utilizing and assembling vane type flow meters in a two way fluid conduit system.
In addition, the previously known vane type flow meters are designed and produced with the indicator positioned so as to be visible from one side only. Thus, when a flow meter is installed in a bypass conduit in which fluid flows in a direction opposite to fluid flow through the main conduit, the indicators face opposite directions. Thus, the position of a viewer must be changed in order to view one or the other indicators since both meters cannot be viewed from the same position unless extensive reengineering and shaping of the bypass conduit is undertaken.